Effects Of GR SiRNA On Proliferation Of MSCs In vitro

Objectives: Bone marrow-derived mesenchymal stem cells (MSCs) are considered a potential attractive source of cells for stem cell-based tissue regeneration. However, the relatively small number and reduced capabilities of MSCs due to in vitro replicative senescence and donor-associated pathophysiological factors severely restrict their potential usefulness in clinical applications.  Glucocorticoids are well-known steroid hormones that regulate MSC proliferation and differentiation. However, the defined effects and underlying mechanisms of endogenous glucocorticoids on MSCs characteristics are not understood.  This study investigated the effects of the blockage of endogenous GCs using glucocorticoid receptor (GR) small interfering RNA (siRNA) on capabilities and senescence of human MSCs in vitro. 

Methods: The proliferation, differentiation and telomere length of human MSCs  were evaluated after blocking the activity of endogenous GCs using GR siRNA delivered by biodegradable poly (lactic-co-glycolic acid) (PLGA) microparticles. 

Results: The results show that PLGA microparticles can serve as a delivery system of GR siRNA and maintain release of siRNA up to 40 days in vitro. Transfection of GR siRNA significantly down-regulates GR and up-regulates the expression of FGF-2 and Sox-11 of human MSCs. MSCs that have proliferated with endogenous GCs blocked in vitro have enhanced proliferation and telomere length and exhibit up-regulated expression of osteogenic markers under differentiation stimulation. Under adipogenic differentiation, MSCs proliferated in vitro with siRNA transfection resulting in significantly lower adipogenic markers compared to controls. 

Conclusions: PLGA particles can serve as a tool for delivery of GR siRNA to effectively block the effects of endogenous GCs on MSCs, which has the potential to improve the capabilities of human MSCs for clinical application by preventing replicative senescence.